A number of different systems exist for the use of people with motor disabilities and verbal disabilities to communicate. An important category of these system are those that allow users to specify a word, phrase, sentence or passage that he or she wishes to say.
Some of the systems that exist today rely on alphabetical representations of words (and therefore, sentences) in order to create sentences. This process is often assisted by word prediction, the use of abbreviations, and the ability to store templates. Nonetheless, many of these systems are slow, language specific, and rely on the ability of a user to understand spelling and grammar.
Other systems are pictorial, and they possess the virtue of being easier to learn and use, and also to establish some degree of language flexibility. Pictorial communication systems are, therefore, popular and widely used amongst the non-verbal community to construct sentences to be spoken out.
There are two approaches to sentence construction with pictures that are in vogue today. The first approach consists of a system where every word in a sentence is stored as a picture, and a sentence is represented by such pictures shown next to one another. Examples of this form of sentence construction are the Board maker software, and the Dynavox system, both developed by Dynavox Mayer-Johnson of Pittsburgh, Pa. Primarily, this system allows the user to map a sentence directly into pictures word-for-word, and therefore, requires nothing more of a user's cognition than the ability to form sentences. In order to store a large vocabulary, however, the system must support a very large number of pictures; for a typical vocabulary used by an adult, it is estimated that more than 3000 words (and hence pictures) are required. This introduces the challenge of categorization, since it is impossible to show all 3000 pictures on a single screen. The user must then be trained to identify the categories and use them appropriately. Likewise, there are several words in most languages that defy categorization and which do not have images associated with them; for example, the words ‘to’, ‘the’ and ‘extra’ would be hard to express as pictures, or fit into a hierarchy of categories. Despite these challenges, the system of single-meaning pictures has been used quite effectively in a number of different applications, mainly by providing the ability to customize categories, classes and templates.
A very different approach to sentence construction with pictures was undertaken by Bruce Baker, who developed the principle of ‘semantic compaction’ through the use of a technology called Minspeak. Minspeak relies on the polysemy of a small set of pictures, which can be used to represent a large set of words. For instance, the picture of an apple may represent (in different contexts) the words ‘apple’, ‘fruit’, ‘red’, ‘eat’, ‘hungry’, ‘gravity’ or ‘computer’. The system of Minspeak uses a small set of such images, which may be combined with other images to uniquely specify words, which are strung together to form sentences. For example, Minspeak allows a system with 144 pictures to represent more than a thousand words, and is claimed by its creator to be sufficient to hold complex conversations. The biggest drawback of Minspeak is the cognitive complexity of the system, which requires users to memorize a large number of combinations of pictures and the words they represent. Minspeak also requires the interlocutor of the user to be familiar with the system, though it is possible to use a microprocessor based system to convert Minspeak icon combinations into words in a language. The complexity of Minspeak is nearly that of a separate language in itself, which has to be taught and learnt in order to be used; therefore, it is not possible for a person with limited cognitive function (such as a mentally retarded child) to use Minspeak effectively.